Planet from the Dune series; the source planet for the Bene Gesserit's original poison drug, or, the "Water of Life", and the origin of the Bene Gesserit order itself.
A planitia is a low plain. On Titan they are named after lanets from the Dune series of science fiction novels by American author Frank Herbert (1920 - 1986).
Image Source. Marker locations are approximate and may not always appear to align with image on map.